The major objective of the proposed research is to elucidate the mechanism of the immunological impairment of the myeloma-bearing host by isolating and characterizing the immunosuppressive soluble factors and by identifying the suppressive cell (B or T cell, macrophage or other). In order to achieve these goals, we have studied the suppressive activity of serum and ascites from tumor-bearing mice and of cell extracts of lymphoid tissue. We are trying to identify the suppressor cell by in vivo transfer experiments and by in vitro co-culturing experiments; and isolate and characterize the suppressive factor by column chromatography (Sephadex G-200, DEAE-Sephadex; and preparative ultracentrifugation in NaBr density gradients). Properties of these fractions will be compared with other immunosuppressive substances. The effect of suppressive cells and/or factors on the immune response will be studied at the cellular and molecular levels by using chemically defined "T"-dependent and "T"-independent clinically relevant antigens, i.e., 2,4-dinitrophenyl (DNP) and pneumococcal polysaccharides (PnSSS) (initially SIII). The effect of factors on the in vivo and in vitro immune response will be determined by a modified PFC test. The antibody response for DNP immune response will be measured by the highly sensitive hemagglutination assay. For PnSSS the sensitive radioimmunoassay will be used, which detects 1-10 micrograms of AbN/ml of serum. The effect of splenectomy and of the tumor on RES clearance of particulate 125I labeled pneumococcal vaccine will be investigated in normal, sham and splenectomized mice in order to further delineate the immunological defect.